The present invention relates to audio effects processors, and more particularly to such processors integrated on a single chip with multiple audio streams.
Audio signal processors are typically included on a sound board or multi-media board in a computer. Such a board will typically connect to the backplane bus and communicate with the host microprocessor. Typical functions included on such a board are the synthesizing of sound, such as by frequency modulation, and the storing and manipulation of audio sound samples. In addition, such boards will typically have a joystick connector for use with video games or other applications. In addition, connectors are provided for a microphone, line-in, a CD-ROM player, speakers, line-out, and a MIDI port.
Typically, multiple chips are included on such a board, such as not only the sound processing chip, but a separate signal processor, a mixer chip for mixing multiple audio signals, a CODEC or one or more analog-to-digital (ADC) and digital-to-analog (DAC) converters, and a frequency modulation sound synthesizing chip (FM chip).
Typically, the mixer would mix sounds in their analog form, with any digital processing being converted to analog form before being provided to the mixer. In addition, the digital processing chip would typically handle one audio stream at a time due to the need to synchronize with a particular audio stream. Digital audio signals may vary slightly, and the signal processing chip may have a phase lock loop (PLL) circuit for synchronizing to the data rate being provided to the chip. When a switch over to another audio source is done, the PLL resynchronizes to the new source.
Digital audio information and other data, such as joystick signals, can be provided to the host processor over the system host bus. One typical type of bus is the PCI bus. The PCI bus includes a standard protocol and requires certain information from any peripheral connected to it for handshaking and identification purposes. Typically, such information is stored in registers in the peripheral device. Included in such information is data identifying a particular board vendor, for instance. Accordingly, manufacturers of sound processing chips will typically have these registers programmed by an EEPROM chip encoded by the particular OEM vendor.
With the increasing demands on sound capabilities with today's computers, it is desirable to have a sound processor which can handle more data streams while minimizing the amount of circuitry required to handle the streams and the number of support chips needed.